n6 THORAX 



of the knife will probably be necessary before a separation can 

 be effected. Divide the right innominate vein and the right 

 phrenic nerve, immediately above the upper end of the superior 

 vena cava, and as the division is made take care not to injure 

 the right vagus, posterior to the vein. Then divide the vena 

 azygos just posterior to its entrance into the superior vena cava. 

 Cut the inferior thyreoid veins, the innominate artery and the 

 left common carotid artery, immediately above the upper border 

 of the left innominate vein, and then if the left innominate vein 

 has not already been divided, divide it in the interval between the 

 left common carotid and the left subclavian arteries. Cut the 

 left phrenic nerve, the superior cervical cardiac branch of the 

 left sympathetic trunk, and the inferior cervical cardiac branch 

 of the left vagus, immediately above the upper border of the 

 aortic arch. 



Next divide the aortic arch. Enter the knife at the upper 

 border of the arch, between the left common carotid and left 

 subclavian arteries and anterior to the left vagus and the left 

 recurrent nerve, and cut from above downwards, completing 

 the division of the arch at the lower border, immediately to 

 the left of the upper end of the ligamentum arteriosum. The 

 left superior intercostal vein will be divided at the same time, 

 but care must be taken not to injure the left recurrent nerve, 

 which is curving round the arch from the front to the back. 

 When the incisions are completed, pull forwards the anterior 

 part of the aortic arch, with the superior vena cava and the lower 

 parts of the innominate veins, and separate them from the lower 

 part of the trachea and from the bronchi. As the separation 

 proceeds, keep the edge of the knife turned towards the aortic 

 arch, to avoid injury to the deep part of the cardiac plexus, which 

 lies anterior to the bifurcation of the trachea. When the lower 

 border of the arch is reached, the twigs which connect the 

 superficial with the right half of the deep part of the cardiac 

 plexus will be exposed, and must be divided. When that has 

 been done, detach the posterior surface of the pericardium from 

 the front of the oesophagus and the descending aorta, taking 

 care to avoid injury to the plexue formed by the vagi nerves on 

 the anterior aspect of the oesophagus. As soon as the separation 

 is completed, the heart, with the remains of the pericardium and 

 the lower parts of the phrenic nerves, can be removed from the 

 thorax, and the investigation of the left atrium and the structure 

 of the heart can be proceeded with ; but, before that is done, the 

 dissector should note that the posterior wall of the pericardium 

 intervenes between the posterior wall of the left atrium and the 

 anterior surfaces of the oesophagus and the descending part of 

 the aorta, opposite the middle four thoracic vertebrae (Fig. 28). 



After the heart and the roots of the great vessels have been 

 removed from the thorax, fasten the left vagus and the recurrent 

 nerve to the part of the arch left in situ by one or two points of 

 suture ; then cut away the remains of the pericardium from the 

 heart, leaving only those portions of it which mark the lines of 

 reflection of the parietal to the visceral portions of the serous 

 sac. Note, as the posterior wall of the pericardium is removed, 

 that it forms the posterior boundary of the oblique sinus (p. 81). 



Atrium Sinistrum. The left atrium, like the right, is 



